remanufacturing in wind power: a multi ...1463409/...wind turbine manufacturing; figure 1 is a...
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REMANUFACTURING IN WIND POWER:
A MULTI CRITERIA DECISION ANALYSIS APPROACH
Dissertation in partial fulfilment of the requirements for the degree of
MASTER OF SCIENCE WITH A MAJOR IN WIND POWER
PROJECT MANAGEMENT
Uppsala University
Department of Earth Sciences, Campus Gotland
Graeme Robertson
05.06.20
REMANUFACTURING IN WIND POWER:
A MULTI CRITERIA DECISION ANALYSIS APPROACH
Dissertation in partial fulfilment of the requirements for the degree of
MASTER OF SCIENCE WITH A MAJOR IN WIND POWER PROJECT MANAGEMENT
Uppsala University
Department of Earth Sciences, Campus Gotland
Approved by:
Supervisor: Sanna Mels
Examiner: Jens Nørkær Sørensen
05.06.20
Abstract
Due to the rapid growth of the wind energy market over the last decade, the future of the
industry will consequently see the dismantling of many wind turbines, both due to wind
turbines reaching the end of their service life and to make way for surpassing technology,
leaving behind a large amount of material that must be dealt with. Furthermore, due to the
advancing technology of wind turbines, there has been a decline in the number of medium
sized wind turbines being manufactured. This study aims to address the problem of future
waste mitigation, whilst attempting to capture the medium scale market. As such, the study
has looked at the idea of transitioning towards a circular economy, in which wind turbines
are not considered as waste at the end of their service life, but rather an opportunity to
recapture value through remanufacturing. This was approached by identifying the driver
and barriers of remanufactured products, utilising knowledge from other industries with
developed remanufacturing sectors.
A Multi-Criteria Decision Analysis (MCDA) has been performed using the PROMETHEE II
method with the objective of drawing a comparison of three scenarios, enveloped by a
theoretical wind turbine selection project. The scenarios were created by the author and
considered the implementation of a new wind turbine and remanufactured wind turbines.
Upon examining the results of the multi criteria decision analysis, it was seen that the
benefits of implementing remanufactured turbines were preferred by the majority of
the stakeholders involved.
Acknowledgements
This thesis has been written as the closing chapter of the master’s course in Wind Power
Project Management at Uppsala University and I would like to express my gratitude to
everyone who has helped me during the process.
To the Wind Energy department, thank you for one of the most interesting and challenging
years of my life. The dedication from all the lecturers throughout the year has allowed me to
leave with a wealth of knowledge, which I can take forward with me throughout my career.
Thank you to my supervisor Sanna Mels for your patience, advice and kind words.
To all my classmates, what a year it has been and what a pleasure it was to spend it with
you all! Thanks to Esma, Jim, Jason, Marc and Andis for all your help and positivity.
Finally, I would like to thank my family for all their support throughout my studies.
NOMENCLATURE
MCDA Multi Criteria Decision Analysis
EOSLWT’s End of Service Life of Wind turbines
NREL National Renewable Energy Laboratory
LCA Life Cycle Analysis
NGO Non-Governmental Organisation
NPV Net Present Value
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Contents 1. Introduction ...................................................................................................................................... 8
1.2. Waste Material ........................................................................................................................ 10
1.3. Potential for a Circular Economy ............................................................................................. 11
1.4. Objectives................................................................................................................................. 11
1.5. Structure of the Report ............................................................................................................ 11
2. Literature Review ............................................................................................................................ 13
2.1. Sustainability ............................................................................................................................ 13
2.2. Triple Bottom Line .................................................................................................................... 14
2.3. Product Lifetime ....................................................................................................................... 15
2.4. End of service life of wind turbines (EOSLWT’s) ...................................................................... 15
2.5. Legislation and guidelines ........................................................................................................ 16
2.6. Circular economy ..................................................................................................................... 18
2.7. Economic potential of circular economy ................................................................................. 20
2.8. End of Life Operations.............................................................................................................. 21
2.9. Remanufacturing...................................................................................................................... 23
2.10. Remanufacturing in wind industry ......................................................................................... 24
2.11. Benefits of Remanufacturing in the wind industry ................................................................ 25
2.12. Introduction to MCDA ............................................................................................................ 27
3. Methodology ................................................................................................................................... 29
3.2. Microsoft Excel ......................................................................................................................... 31
3.3. PROMETHEE II .......................................................................................................................... 31
4. Project Description .......................................................................................................................... 34
4.2. Case Study ................................................................................................................................ 34
4.3. Life Cycle Analysis Review ........................................................................................................ 34
4.4. Scenarios .................................................................................................................................. 36
5. Stakeholder Selection ..................................................................................................................... 37
5.1. Investor .................................................................................................................................... 37
5.2. Developer ................................................................................................................................. 37
5.3. Public ........................................................................................................................................ 38
5.4. Environmental NGO ................................................................................................................. 38
5.5. Manufacturers ......................................................................................................................... 38
5.6. Governmental body ................................................................................................................. 38
6. Evaluation Criteria ........................................................................................................................... 39
6.1. Economic Criteria ..................................................................................................................... 39
6.1.1. Manufacturing Costs ............................................................................................................. 39
6.1.2. Net Present Value ................................................................................................................. 40
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6.1.3. Environmental Criteria .......................................................................................................... 40
6.1.4. Material Circularity Indicator ................................................................................................ 40
6.1.5. Energy to Manufacture ......................................................................................................... 42
6.1.6. Co2 to Manufacture .............................................................................................................. 43
6.2. Technical Criteria ..................................................................................................................... 43
6.2.1. Availability ............................................................................................................................. 43
6.2.2. Risk ........................................................................................................................................ 44
6.2.3. Lead Time .............................................................................................................................. 44
6.2.4. Product Development ........................................................................................................... 45
6.3. Social Criteria ........................................................................................................................... 45
6.3.1. Perceived Quality .................................................................................................................. 46
6.4. Summary of Criteria ................................................................................................................. 46
7. MCDA Results .................................................................................................................................. 48
8. Discussion ........................................................................................................................................ 52
8.2. Analysis .................................................................................................................................... 52
8.3. Limitations................................................................................................................................ 53
9. Conclusion ....................................................................................................................................... 54
9.1. Summary of the study .............................................................................................................. 54
9.2. Future Research ....................................................................................................................... 55
10. References .................................................................................................................................... 56
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List of Figures Figure 1:Top 10 onshore turbine manufacturer’s, 2016 (GW)(BNEF, 2016) ____________________________ 10Figure 2:Adaptation of waste hierarchy, taken from Ellen McArthur Foundation (ellenmcarthurfoundtion.org, 2017) ___________________________________________________________________________________ 17Figure 3:Illustration of linear economy's 'take-make-dispose' nature (ellenmcarthurfoundation.org 2017). __ 19Figure 4:Material flow in a circular economy (ellenmcarthurfoundation.org 2017) _____________________ 20Figure 5:Case studies of companies utilizing closed loop supply chain (Ellen McArthur Foundation, 2014) ___ 21Figure 6: Illustrative flow chart of the methodology ______________________________________________ 30Figure 7: Preference of Investor ______________________________________________________________ 48Figure 8: Preference of Developer ____________________________________________________________ 48Figure 9: Preference of Public ________________________________________________________________ 49Figure 10: Preference of Environmental NGO ___________________________________________________ 49Figure 11: Preference of Manufacturer ________________________________________________________ 50Figure 12: Preference of Governmental Body ___________________________________________________ 50Figure 13: Summary of preferred scenarios _____________________________________________________ 51
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List of Tables Table 1: Criteria Weighting. _________________________________________________________________ 32Table 2:Summary of components and average mass from LCA’s reviewed. ____________________________ 35Table 3:Summary of materials and average material mass from LCA's reviewed. _______________________ 35Table 4: Scale of Turbine Availability __________________________________________________________ 44Table 5: Scale of Encouragement of Sustainable Design ___________________________________________ 45Table 6: Scale of Perception of Quality _________________________________________________________ 46Table 7: Summary of Criteria ________________________________________________________________ 47
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1. Introduction 1.1. Growth of Wind Power
Recent years have seen the commitment of EU countries to an energy agreement which aims
to reduce greenhouse gas emissions by 40%, whilst increasing the consumption of renewable
energy to at least 27%. In 2016, wind power in Europe accounted for 10.4% of energy
consumption and 51% of the total installed power generation; globally however, it was China
that were making the biggest movement in the market, taking a 42.8% share of the global
installed market for the same year. With an increase in market growth, comes the increase in
wind turbine manufacturing; Figure 1 is a representation of the current top 10 onshore wind
turbine manufacturers.
Figure 1 is a representation of the manufacturing market leaders in 2016 with Vestas, GE
and Goldwind commanding the market of the installed capacity and the 2017 merger of
Siemens and Gamesa will result in the big three, becoming the big four.
1.2. Waste Material
The decommissioning of modern wind turbines is a relatively new process, but due to the
rapid growth of the market over the last decade, the future of the industry will consequently
see the dismantling of many wind turbines, both due to wind turbines reaching the end of
their service life and to make way for surpassing technology, leaving behind a large amount
of material that must be dealt with. Some estimates show that total waste material will
Figure 1:Top 10 onshore turbine manufacturer’s, 2016 (GW)(BNEF, 2016)
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increase an average of 12% per year between 2014 and 2026 and 41% per year between 2026
and 2034 (Anderson et al). To minimise the footprint on the earth, there are several ways in
which material can be handled; coupled with government legislation, wind turbine owners
have greater responsibility to handle the material in an environmentally sound manner. This
is resulting in a transition from a product life cycle which is linear, make, use, dispose, to a
more circular life cycle, in which the product remains in use either in full form or as a separate
product.
1.3. Potential for a Circular Economy
Circular economy is a concept which envelops the ideas and processes that are designed to
create a continuous improvement of today’s society, with the aim of utilizing the potential of
all products, components and materials, resulting in a reduction in the amount of material
and energy that is wasted to meet current human demand. Aside from the environmental
benefits a circular economy can provide, there is also the potential for companies to strive
economically, and products or services to be developed towards a more sustainable future.
1.4. Objectives
The objective of this report is to address the future waste issue within the wind energy
industry and seek for options to minimise its impact on the environment. The author aims to
look towards remanufacturing as a potential resolution to the problem by assessing the
drivers and barriers of remanufactured wind turbines; through the creation of a theoretical
project, a MCDA (Multi criteria decision analysis) will be carried out to make an evaluation of
the selection process between a remanufactured wind turbine and a new wind turbine. This
has led to the following research questions:
What are the driving factors for remanufacturing within the wind energy industry?
Using MCDA, how do these factors affect the outcome of the turbine selection process?
1.5. Structure of the Report
Chapter 2 of this paper presents a literature review deemed relevant to the end of service life
of wind turbines (EOSLWT’s) and the future potential of sustainability within the wind energy
industry as well as the implementation of MCDA in sustainable energy projects. This review
has enabled a better understanding of the benefits and barriers regarding the sustainable
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management of decommissioned wind turbines as well as identifying an appropriate tool to
compare the authors findings. Chapter 3 presents the methodology for the study, giving an
insight to the approach taken by the author with a description of the tools used, including
detailed description of the MCDA method PROMETHEE II. Chapter 4 outlines the theoretical
case study which the author has developed to compare the findings of the literature review.
The results from the study will be provided in chapter 5 before a conclusion and discussion of
the study, including potential future research in chapter 6.
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2. Literature Review
There are an increasing number of publications arising which reflect on EOSLWTs and the
issues involved. This literature review was carried out with the intention of reviewing
publications that cover several topics that are both directly linked to EOSLWTs and future
waste material, as well as the end of life opportunities that are currently available such as
reuse, recycling and remanufacturing. Furthermore, publications that explore the idea of
working towards an altogether more sustainable, circular economy were also reviewed.
2.1. Sustainability
Humans, per capita, are filling land fill sites at a faster rate than the planet can accommodate
and are consuming more resources than the planet can reproduce, notably more so in
Northern industrialised countries as well as large cities in Southern countries (Princen 1999).
Humanity’s Ecological Footprint is a measurement, which aims to compare human
consumption of renewable resources and ecological services against natures ability to supply
them (Rees, 1996) a recent study has calculated that it had exceeded the Earth’s total bio-
capacity, the regenerative ability of nature’s resources, by more than 60 percent in 2012
(WWF, 2012). Alongside growing population and technology, rising consumption is one of the
three major causes of changes in the global environment which provoke warning signs of the
potential for even larger footprints in the future (Princen, 1999).
The need to take responsibility and combat this problem has been growing over the past
few decades, leading to the concept of sustainable development, which was first coined
in the Brundtland Report in 1987, with the following definition;
‘development that meets the needs of the present without compromising the ability of
future generations to meet their own needs’ (WCED, 1987).
Following its release in 1987 there has been a plethora of modified definitions of
‘sustainability’ and ‘sustainable development’, with an estimated three hundred definitions
currently existing within the disciplines that are either directly or indirectly related (Johnston
et al, 2007). This is due to imprecise designation and recognition of sustainable development
terminology as well as different term usage depending on geographical area (Glavič et al,
2007). However, amongst the many interpretations of sustainability and what
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it encompasses, there are two recurring themes throughout the literature; the first theme,
introduced in the Brundtland (1987) report, is the theory that sustainable development is
allowing today’s generation to meet their needs without affecting future generations ability
to meet theirs. The second theme, also present in the report is that if progress is to be truly
sustainable it must address environmental, economic and social aspects simultaneously to
succeed. Incorporating both themes for a combined interpretation would suggest the
following definition: Addressing economic, environmental and social factors to meet the
needs of today, without affecting future generation’s ability to meet theirs. Such terminology
has ultimately lead to the development and creation of the term ‘triple bottom line’ or, the
‘three pillars’ of sustainability.
2.2. Triple Bottom Line
Triple Bottom line is a term developed in 1994 by Elkington (1998) due to the
understanding that to make real environmental progress the social and economic
dimensions, which had been flagged in the Brundtland Report previously, would have to
be addressed in a more integrated way (Henriques 2004). In the first chapter of Enter the
Triple Bottom Line, written by Elkington, he states that the term of TBL came about
through no single moment of realisation “...instead, in 1994 we had been looking for new
language to express what we saw as an inevitable expansion of the environmental agenda
that sustainability had mainly focused upon to that point”.
The concept is based on the idea that an organisations performance should be measured in
relation to all stakeholders, including local communities and governments, not just the
stakeholders with whom it has direct relations with, such as employees, suppliers and
customers (Hubbard, 2009). It is believed that many organisations find the concept of TBL
untoward, as it suggests that the common company responsibilities go much further than
simply producing products and services that customers want for economic benefit, by
incorporating social and environmental aspects as well (Hubbard, 2009). However, the Triple
Bottom Line suggests that when economic, environment and social performance intersect,
the company has the ability to have a beneficial effect on society and the natural environment
whilst simultaneously achieving long term economic benefits, as well as providing a
competitive advantage over other companies (Carter et al, 2008).
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2.3. Product Lifetime
The definition of the life time of a product can be unclear with the exact beginning and
end of a products lifetime proving to be a grey area. The lifetime of a wind turbine is more
commonly referred to as the ‘service life’ due to the nature of the products function. The
definition of service life can be defined as follows: ‘the period from when a product is
acquired until the moment it is disposed of’ (Cooper, 1994).
2.4. End of service life of wind turbines
For wind turbine’s the product lifetime refers to the moment of commissioning until the
moment of decommissioning. Cooper et al (2010) distinguishes further definitions which
are appropriate to the wind energy industry:
1. The technical lifetime being the maximum period a product has the physical
threshold to function.
2. The replacement or economic lifetime being the period from initial sale to the point
where the owner buys a replacement regardless of the product functioning or not
(Cooper, 2010).
As a turbine nears its end of life, its performance begins to deteriorate, due to mechanical,
environmental and technological ageing and therefore, in most cases, it becomes
uneconomical for it to continue operating. It is at this stage where the owner/operator has a
responsibility to decommission the turbine(s) as part of their ongoing commitment to its
initial development. It has become customary practice to have decommissioning plans
submitted as part of the initial project plan and environmental impact assessment, where
financial security for the decommissioning project must be established through a bond, which
will cover all or part of the costs; it is noted that the sum required, as well as who is responsible
for its management, varies between and within countries (Alden et al, 2014). The UK Energy
Act (2008) requires developers to demonstrate that payment to the decommissioning fund is
evident in the annual returns, ensuring transparency and minimising risk to the tax payer
(Scottish Government, 2008)
Full or partial decommissioning, for both onshore and offshore wind turbines, must be
considered by the owner, where the former involves returning the site back to its previous
state, and the latter can result in components, such as foundations or cables, remaining on
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site, under conditions that it causes minimal disruption to the surrounding environment and
habitat. In either case, it is important to consider the way the site is decommissioned, and the
decommissioning plan should consist of habitat and protected species surveys as performed
in pre-development environmental impact assessments. The subsequent dismantling of the
wind turbine(s) of course leads to an inventory of components and material which the
responsible party must manage.
Many current publications express the concern regarding the growth of the wind industry and
relative inexperience when it comes to end of service life (EOSL) (Andersen et al, 2016.,
Andersen et al, 2007., Ortegon et al, 2013., Topham et al, 2016). However, there is a distinct
lack of research on the technological, environmental, and economic issues associated with the
EOSLWT’s, because of its past subservience. It is noted that this is due to the relative infancy
of the industry, resulting in next to no historical data available for use (Ortegon et al, 2013).
The publication by Andersen et al (2016) attempts to address these concerns by quantifying
future waste material, expressing the importance of ensuring there is sufficient recycling
capacity. The study is specific to the growth of the wind industry in Sweden and the
subsequent increase in wind turbine waste over the next two decades; it estimates that total
waste material will increase an average of 12% per year between 2014 and 2026 before taking
a dramatic spike to an average of 41% per year between 2026 and 2034. This increase in
estimated waste is relevant to the growth of the wind industry around a decade before now,
which resulted in the annual increase of installed capacity.
2.5. Legislation and guidelines
There are several legislations and guidelines that developers must adhere to when deciding
how to manage the material accumulated from decommissioning, and developers are obliged
to create a site waste management plan as part of these requirements (Scottish Government,
2008). An example of such is when in 2010, the Scottish Government published its Zero Waste
Plan, intended to provide guidance through a waste, economic
and resource strategy in support of their aim of achieving a ‘zero waste’ society. It envelops
22 actions that will help to deliver the Zero Waste vision of Scotland:
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• ‘where everyone – individuals, the public and business sectors - appreciates the
environmental, social and economic value of resources, and how they can play
their part in using resources efficiently;
• reducing Scotland’s impact on the environment, both locally and globally, by
minimising the unnecessary use of primary materials (materials in their first life
cycle; raw materials), reusing resources where possible, and recycling and
recovering value from materials when they reach the end of their life;
• about helping to achieve the targets set in the Climate Change (Scotland) Act 2009 of
reducing Scotland’s greenhouse gas emissions by 42% by 2020 and 80% by 2050;
• to contribute to sustainable economic growth by seizing the economic and
environmental business and job opportunities of a zero waste approach’ (Scottish
Government, 2010).
Multiple countries have adopted similar regulations in an attempt to coerce organisation’s
into taking more responsibility for the impact they are having on the environment. It
encourages the idea of sustainable development as aforementioned in Chapter 2.1.
This concept is further echoed by ‘The waste hierarchy’, which refers to the ranking system,
set out by the European Waste Framework Directive, for the management of waste material
(European Parliament 2008/98/EC), and can be considered the foundations of which the
Scottish Government sets its waste regulations on. It is intended to have a positive impact on
waste prevention and reduce the amount of waste that is being sent to landfill. Figure 2
represents the waste hierarchy in ascending order.
Figure 2:Adaptation of waste hierarchy, taken from Ellen McArthur Foundation (ellenmcarthurfoundtion.org, 2017)
1. Prevention of waste: A factor that aims to directly reduce the amount of material
entering circulation. This can be done through the design of product which require
less material, and the use of less hazardous materials.
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2. Preparing for reuse: Involves the inspection, cleaning, repairing and refurbishment
of products or components, to be re-entered into the product life cycle in a
functional condition.
3. Recycling: The action of turning waste material in to a substance or new product,
effectively giving the material a new life.
4. Other recovery: Such as energy recovery is where the material can no longer be
used for practical purposes and therefore is processed by means of gasification or
pyrolysis to produce fuel, heat and power as an energy source.
5. Disposal: When the material has no further potential, and is sent to landfill or
incinerated without recovery, and is the last resort is regards to the waste hierarchy.
Similar plans have been developed throughout Europe and the planning of wind
power projects must adapt to these and further changes in legislation that will no
doubt arise in years to come (ellenmcarthurfoundation.org 2017).
2.6. Circular economy
The Circular economy is a concept which envelops the ideas and processes that are designed to
create a continuous improvement of today’s society, with the aim of utilising the potential of all
products, components and materials, resulting in a reduction in the amount
of material and energy that is wasted to meet current human demand. Its emergence is owed
to the flawed linear ‘take-make-dispose’ model, represented in Figure 3, which society has
adopted, where continuous, copious amounts of energy and resources are used to create
consumables which are disposed of when there are deemed unfit for purpose.
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Figure 3:Illustration of linear economy's 'take-make-dispose' nature (ellenmcarthurfoundation.org 2017).
Stahel (1998) addresses this linear model adding that terms such as ‘value added’, the point of
production, ‘value write off’, the depreciation of value after sale and ‘waste’, the end of the
product life, only amplify the need for a change in the way we operate as responsibility for the
product does not leave ‘the factory gate’. A circular economy addresses these issues by creating
an industry which is ‘restorative and regenerative by design’. It is noted that there is no single
origin of the concept of a circular economy however it began gaining more recognition for its
implementation on the modern economic systems and industrial processes during the 1970’s
(Ellen McArthur Foundation, 2017).
The Ellen McArthur Foundation is an organisation founded by Dame Ellen McArthur, which
aims at promoting this concept, describing it as ‘a potential way for our society to increase
prosperity, while reducing dependence on primary materials and energy” (Ellen McArthur
Foundation, 2015). Figure 4 shows the cyclic model which is an adaptation of the drawing from
McDonough et al (2002) book “Cradle to Cradle”. It illustrates the three principles
considered to be essential to a circular economy, looking at both the biological and technical
material flow through what is labelled the “value circle” as seen in Figure 4 below.
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Figure 4:Material flow in a circular economy (ellenmcarthurfoundation.org 2017)
2.7. Economic potential of circular economy
Further to the environmental benefits of a circular economy, there are publications that look
at the potential economic opportunity which lies within products that can have recoverable
value. Closed loop supply chains refer to the recovery of products or their components within
one system to reuse for further value. A definition of this can be considered as “the design,
control, and operation of a system to maximize value creation over the entire life cycle of a
product with the dynamic recovery of value from diverse types and volumes of returns over
time. (Guide and Van Wassenhove 2006, Managing product returns for remanufacturing).”
The reason for such potential of recoverable value is detailed in the publication Towards
the Circular Economy 3: Accelerating the Scale (2014), which suggests that economies,
companies and consumers will all benefit from such a strategic shift. It further describes
that the reduction in material and energy costs as well as a more stable hand on material
volatility and supply chain risks would see economies flourish. Companies would benefit from
secondary markets and “competitive advantage”, whilst consumers would reap the benefits
of improved choice and better service quality”. The publication further emphasises the
potential to create more resilient economies through better material productivity, and the
evolution from the current low skilled “mass production” labour to one with a much higher
skill set, which will signify a move that would make it harder to revert to the linear economy.
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The publication by Atasu (2008) takes a broader look at the economic benefits of a closed
loop supply chain, explaining that many publications simply assume that product retrieval and
its reusable quality thereafter, is often considered a formality. Geyer et al (2007) further state
that even with the quality of the product remaining at the standard of its first life, there are
many other factors that are required for a closed loop system to be profitable, such as a
steady used product collection rate, durability and product life cycle.
Towards the Circular Economy 3: Accelerating the Scale Up gives recognition to the
importance of collection and reverse logistics to improve material productivity and provides
case studies of companies that have successfully been able to use a closed loop system to
their benefit economically (Ellen McArthur Foundation, 2014). An example of the case studies
is provided as reference in Figure 3.
Figure 5:Case studies of companies utilizing closed loop supply chain (Ellen McArthur Foundation, 2014)
2.8. End of Life Operations
Reuse, recycling, repair, reconditioning and remanufacturing are the five general terms
encompassing techniques which can help achieve sustainable development (Ijomah, 2010).
Ijomah (2010) categorises remanufacture, reconditioning and repair as ‘addition’ processes
that use components from used products, also known as; component reuse, product recovery
22
or secondary market; since they typically involve some degree of disassembly they are further
referred to as disassembly processes. These processes are generally preferable to recycling,
which is the process of collecting, sorting and processing discarded materials to use in the
production of new products. The paper elaborates further, listing the advantages that product
recovery strategies have over recycling. These include; bringing products back to working
order through product recovery, which is adding value to waste whereas recycling reduces
products to its raw materials. Product recovery also attempts to keep products as whole as
possible, which reduces the overall energy and resources. When recycling, all the energy and
resources are lost from the initial manufacture with potential to use significantly more energy
in raw material extraction, transportation and processing of these reclaimed raw materials
to make new products. Product recovery retains the energy used in the initial
manufacture (King et al, 2006). Considering the reuse at the end of life of a product whilst
designing can allow producers to effectively meet the environmental, legislative and
competitive needs through the following:
• Increasing product life, meaning it takes longer before the product is discarded.
• Enabling servicing of products at the end of use, so that they can be used again.
• Enabling materials of the product to be recycled and used to make new ones if not
suitable for product recovery or reuse.
• Enabling used components to be used in new products.
Ijomah et al (2004) hypothesised that the ambiguity surrounding the definition of
remanufacturing and the inability to differentiate between the strategies was a major barrier
that was impeding the uptake of product recovery and re-use processes in industry. The
research conducted produced a robust definition as well as establishing the distinct differences
between remanufacturing, reconditioning, repair and recycling including the work content
required. The concluding definitions of the research are detailed:
“Recycling: Reducing a used product to the value of its component material, though
complete disassembly and processing.
Remanufacture: Returning a used product to original or improved specification with a
warranty that matches or is greater than the new component; through inspection,
disassembly, cleaning, reprocessing, reassembly and testing.
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Reconditioning: Returning a used product to satisfactory condition through the
replacement of faulty or worn components. Commonly with a warranty less than that
of the new equivalent.
Repair: Fixing identified fault within a product to return it to working condition.
Warranties generally only cover the repaired part and are less than that of new
equivalent products.”(Ijomah et al. 2004)
2.9. Remanufacturing
Throughout the literature relating to sustainable manufacture, the concept that presents
itself most often is remanufacture. The publication by Andersen et al (2007) notes that the
future handling of material is unclear, suggesting that recycling will be the more prominent
process. As can be seen in the waste hierarchy (Figure 1), this disregards the potential there
is for a more sustainable handling of the material through prevention and reuse. Multiple
authors agree that remanufacturing is the preferable end of life process as it adds value to
products that may have been scrapped; helps to reduce landfill; reduces the level of required
virgin materials as well as reducing the energy levels required in the manufacturing phase
(Ijomah et al.,2004; Hatcher et al., 2011; King et al. 2004). Cooper (2010) adds that with the
aim of reducing the amount of material used within a process as well as energy demands, an
approach which doesn’t rely on recycling and instead, encourages product life extension,
should be applied. Hazen et al (2016) describes remanufacturing as “the ultimate form of
recycling”. A common understanding of the need for a clear definition of remanufacturing is
prominent throughout the literature reviewed (Ijomah et al, 2004., Ortegon et al, 2014). As
a reminder the definition of remanufacturing implies that a product that has been used and
therefore, considered to be at the end of its useful life cycle, is given a new life which
emulates the quality of its previous life through the dismantling, cleaning, repairing and
replacement of components and reassembly. This also means that after testing, it should
have a warranty that matches the product in its first life.
Many publications acknowledge Xerox as being a prime example of how companies can
effectively use remanufacturing to their advantage (Statham, 2006., King et al, 2006). The
company initially delved in to a new project they called “asset recovery” in 1987 by creating
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an entirely different subsidiary to their plant in the Netherlands, which had the aim of
retrieving old photocopying machines from the waste stream and to then process these
machines for resale. A successful venture which saw 75% of the machines being
remanufactured within a decade and even though the remanufactured machines were
competing on the market with the new machines that Xerox were producing, a saving of
$95M over the decade was made. A further example of successful remanufacturing, which
was depicted in Figure 3 Is that of Caterpillar, who have had an involvement in
remanufacturing since the 1970’s. They now claim to “provide customers with lower-cost
products, shorter downtime and quick, dependable service options”. It is not just the benefits to
customers and their business which has driven the company to expand their remanufacturing
programs, stating “we make one of the greatest contributions to sustainable development—
keeping non-renewable resources in circulation for multiple lifetimes.” This is a fitting example
of a company’s early embodiment of a circular economy.
2.10. Remanufacturing in wind industry
As the market for remanufacturing stands in wind power just now, companies who specialise
in remanufacturing look to procure used wind turbines before remanufacturing and selling
for profit. While there are used turbines currently available on the market, the process has
somewhat more uncertainty to it, as the original manufacturer is not simply collecting the
used turbine at the end of service life. This is not to say that the big players are not getting
involved in remanufacturing. Vestas and Caterpillar came to an agreement in 2011, which
would see the remanufacturing giants do what they do best on wind turbine components.
This allows Vestas to then sell their remanufactured components as part of their “spares and
repairs” department which is a positive move towards a circular economy
(windpowermonthly.com, 2017).
The study by Ortegon et al (2014), notes the potential for the medium size turbines market,
stating that this usually consists of turbines between 500kw-1500kw, however the study by
Walton and Parker (2008) suggests that the production of medium scale wind turbines has
slowed significantly due to the industry’s continuous scaling up where the focus is on
designing larger wind turbines with the main aim of creating larger profit margins.
Nonetheless, they predict that the market will become more prominent, with an estimated
25
2000 units per year coming available by 2024. The main sectors that would consume this
market are those who are looking to make significant electricity cost savings, such as
communities, farmers, industrial plants and schools; all of which have already began to look
to wind power as a resolution (Parker et al, 2008).
2.11. Benefits of Remanufacturing in the wind industry
While the studies suggest there is the potential for remanufacturing to flourish with in the
industry, it is important to understand the benefits it would provide. Although the
ideologies of remanufacturing, such as the reduction in raw material usage and waste
prevention, are presented in previous sections of this literature review, the specific
impacts that it would have within the wind industry must be clarified.
Parker et al (2008), state that significant cost savings could be made from remanufacturing a
wind turbine rather than the purchase of a new unit. This is primarily down to the potential
saving in initial investment which is a key driver to the development of a wind power project.
Due to the lack of practice, or more specifically, research, on the economic benefits of
remanufacturing within the wind industry, it is difficult to provide detailed economic data on
the reduction in manufacturing costs; Ortegon et al (2014) notes that the current supply of
remanufactured turbines cost between 30-50% of that of a new turbine, a saving which can be
presumed to be down to the cost savings made from the processing of raw materials and
manufacturing of components. Further economic benefit can be found from the difference in
lead times to produce a remanufactured turbine to that of a new one. A report from NREL
(2004) state that the lead times for new wind turbines can be anything from 12 to 16 months,
where some remanufacturers are promoting a lead time of less than three months
(repoweringsolutions.org, 2017., PES Wind, 2017). The author has noted that this lead time
could be down to the high demand of new wind turbines compared to the low demand of
remanufactured wind turbines and this would most likely have to be reassessed as a benefit
should the remanufacturing market increase. However, the potential for reduced project
duration would be a key driver for the medium scale market.
As aforementioned, there are many industries which have a well-developed remanufacturing
sector and so potential energy savings of remanufacturing are somewhat better researched.
A study by Sutherland et al (2008) compares the energy intensities between the
26
manufacturing and remanufacturing of diesel engines and reports energy savings of almost
90% compared to an engine manufactured from virgin material. Other literature based on
remanufacturing from multiple industries provide an overall average energy consumption
value of around 50% of that of a manufactured product. It is worth
noting that due to the high-performance requirements of wind turbines, there are several
components which will experience a high level of wear and tear during the lifetime of a wind
turbine. Any component which is exposed to the environment, such as the blades, will fall in
to this category as well as all moving parts that undergo an almost continuous amount of
stress such as the gearbox (PLATE, 2017). The study by Ortegon et al (2014) states that regular
maintenance of wind turbines will help to substantially reduce the risk of failure, while
bringing down maintenance costs and downtime.
There is room for improvement when it comes to the design of wind turbines. Inheriting a
design which makes maintenance or replacement of components a much simpler task would
be beneficial in further reducing financial risk of a wind turbine failing. The study by Charter et
al (2008) concluded that it is the design stage of a products lifespan which will have the
greatest impact on the cost, manufacturing and end of life possibilities.
Growth Within: A Circular Economy Vision for a Competitive Europe presents the idea that
such design activities would be further developed if companies were to share their
product information, ultimately leading to greater utilisation of products, development of
secondary markets and driving the markets economy and competitiveness. In turn, the
greater utilisation of products would lead to an optimisation of material circularity and
improvement on product design. The study concludes these thoughts by posing two
questions for companies:
If your products were designed for take-back, how much value could you
recapture from products sold?
If you had to take back all the products you sell, how would that affect design and
production?
This displays a perfect example of how the rethinking of the way products are designed could
prove beneficial to a company’s, and an industry’s economic growth. (Ellen McArthur
Foundation, 2015). As previously noted, remanufactured products are considered to emulate
the quality of its first life, however, multiple studies note that consumers, retailers
27
and even remanufacturers do not perceive equality between them, suggesting that their
behaviour towards remanufactured product is altered (Hazen 2016.; Smith et al, 2008). Hazen
(2011) provides explanation by saying the consumers may see the remanufacturing process as
ambiguous, with particular uncertainty in the products past life as well as the necessary actions
required to bring the product back to original quality. Hazen et al (2016) goes on to note that
the perceived quality of a product is a multidimensional concept, which takes in to
consideration the products lifespan, features, performance and serviceability. Due to this
uncertainty on the product, studies on consumers “willingness to pay” have been conducted,
and it was concluded that when a remanufactured products cost is more than 70% of a new
product, the consumer would opt to buy the latter (Gan et al 2017).
2.12. Introduction to MCDA
As development of sustainable energy grows, many developers are turning to multi-criteria
decision analysis (MCDA) tools to help with the decision-making process of their projects. As
Wang et al (2009) notes, “MCDA is a form of integrated sustainability evaluation” and the reason
for its rise in popularity in the development of renewable energy is due to “the multi-
dimensionality of the sustainability goal and the complexity of socio-economic and biophysical
systems”. The study supports its use due to its ability to minimise the difficulty of the decision-
making process through comparison of influential, yet conflicting criteria, that have differing
data and perspectives. Georgopoulou et al (1997) goes on to express that the conflicting
criteria doesn’t simply show the multicriteria nature of sustainable energy, but also the need
to account for the interest of multiple stakeholders. This is echoed by Georgopoulou et al
1997., Mateo 2012) who notes that every new stakeholder that is involved will result in the
addition of new criteria and subjective opinions, which must be considered. He notes that the
stakeholders involved vary from investors, individuals, institutions, authorities, environmental
groups and governing bodies, all of which may have interests which directly or indirectly affect
the process of decision making. The aim of this study is to draw an outcome from one decision
within such projects, the selection of a wind turbine, with the focus on the reduction of waste
material through the utilisation of remanufactured turbines by comparing the economic,
environmental, technical and social criteria that would affect the decision-making process.
28
There are several MCDA tools that have been used in the sustainable energy planning, which the
study by Watrobski et al (2016) have outlined in their study. They concluded that analytical
hierarchy process (AHP) was the most common tool used with analytical network process (ANP),
a generalised version of AHP also present. The study noted that these tools only allow for
qualitative data to be analysed, with the evaluation of quantitative data being sacrificed. Other
methods used were Technique for Order of Preference by Similarity to Ideal Solution, Simple
Additive Weighting or Ordered Weighted Averaging Aggregator (OWA) as well as the preference
ranking organization method for enrichment evaluation (Behzaidan et al, 2010). PROMETHEE II
is a further developed method from its predecessor PROMETHEE I which is said to be a more
comprehensive approach to decision making (Brans & Vincke, 1985).
Behzadian et al (2010) presents PROMETHEE II as a means of providing a ranking, from a finite
set of alternatives from the most preferred to the least. The fundamental working of
PROMETHEE II is to make pairwise comparisons of the alternatives against each of the
selected criterion (Behzaidan et al, 2010). PROMETHEE II has been used in this study on the
basis that it has been well implemented in previous studies which look at the development of
renewable energy projects; this is owed to its ability to relay conflicting economic,
environmental, social and technical data to decision makers, who may not be well rehearsed
in MCDA techniques, in a clear and concise manner (poladitis 2006, georgopulou). Further
description of the tool can be found in section 3.3.
29
3. Methodology
3.1. Introduction
This chapter provides a description of the methodology used to complete the study with
further detailed description of the tools. The aim of this study is to assess the possibilities for
minimising the amount of material that will be wasted from future decommissioned wind
turbines through alternative end of life strategies. From the literature studied it was noted
that there was potential for developing a remanufactured market within the wind energy
industry. Upon this finding the author has decided to compare the driving factors of selecting
a remanufactured wind turbine rather than a new wind turbine. The focus is on the potential
for minimising the environmental effects that the industry in the future and the criteria of this
study reflect this. The MCDA tool which has been used is PROMETHEE II after research
showed that it has been successfully implemented in to projects within sustainable energy.
Furthermore, its straightforward application and comprehensive comparison of results
provide a clear outcome.
The wind energy industry is continuously seeing the improvement of wind turbine
performance; a noticeable attribute of recent technology is the physical growth of the
wind turbines. This has led to the depleted manufacturing of medium scale wind turbines
even though there is an ever-increasing market that would benefit from them, such as
communities, farmers and industrial companies. Furthermore, the market for
decommissioning wind turbines is set to rise drastically over the next few decades as we
see initial wind energy projects near the end of their service life meaning that there will
be a substantial amount of material that must be dealt with.
In an attempt to address both of these problems comparison of a wind turbine selection
process will be carried out and from the information gathered on the subject of
remanufacturing, and its potential implementation in to the wind energy sector, three
scenarios have been created. The identification of all the stakeholders that are affiliated
with a wind power project are considered before further refinement applied to suit the
objective of the study.
With thought given to the stakeholders involved, a list of possible criteria is created. This list
concentrates of driving factors that would directly impact the decision between the scenarios
30
and therefore are relatable to manufacturing and remanufacturing. The criteria can be
divided in to four categories; economic, environmental, technical and social. Following this,
the data collected for the criteria as well as the preference of all stakeholders can be
processed using PROMETHEE II with the outcome being the understanding of the preferred
scenario for each stakeholder. A representation of this methodology can be seen in figure 4
Figure 6: Illustrative flow chart of the methodology
31
3.2. Microsoft Excel
Data for many of the criterion was collected from several studies which had researched
the topic of remanufacturing. To apply the information gathered to this study, the author
has used Microsoft Excel to carry out calculations for some of the qualitative criteria. More
details of the relevant calculations can be found in Section 6.
3.3. PROMETHEE II
As Behzadian (2010) presents, the aim of PROMETHEE II is to provide a ranking from a finite
set of alternatives from the most preferred to the least. The fundamental working of
PROMETHEE II is to make pairwise comparisons of the alternatives against each of the
selected criterion. In this study he breaks down the working of PROMEETHEE II in to five clear
steps and so this study will follow the same approach. Before entering data in to the
PROMETHEE II method, the user must have assigned weighting to each of the criterion
selected. Ideally, the weighting of assumptions would involve the stakeholders input,
however, due to the lack of stakeholder availability, and for continuity, the author has decided
to weight the criteria based on assumptions, focusing on their main goals when considering
a project such as this. As can be seen in Table 1, the weighting of the criteria was created
using 100 points for each stakeholder across the 7 criteria. Each stakeholder’s preferences
differ and so the weighting of the points is solely based on their input, with no influence on
other stakeholders. This means that while stakeholder A may find a criterion 1 more
important than stakeholder B, Stakeholder A may also consider multiple other criteria of high
importance, which could lead to stakeholder B having a higher point score for criterion 1. A
list of the selected criteria and their weighting for the following study can be found in table 1.
32
Table 1: Criteria Weighting.
Criteria Direction Investor Developer Public
Environmental NGO's
Manufacturers Governmental Body
Manufacturing Cost Min 22 16 17
2 18 8
NPV Max 23 15 13 2 3 2
MCI Max 2 3 8 23 13 14
Energy to Manufacture Min 2 5 8
20 11 17
Co2 to Manufacture Min 2 5 10
22 11 17
Availability Max 6 13 2 4 7 7
Risk Min 18 15 13 3 2 16
Lead Time Min 8 16 2 4 18 6
Product Development Max 2 4 8
18 10 7
Perceived Quality Max 15 8 19
2 7 6
Total 100 100 100 100 100 100
As aforementioned, the first step of the PROMETHEE II calculation is to perform the pairwise
comparisons, as denoted by Equation 1.
��(�, �) = ��(�) − ��(�)
Where ��(�, �) denotes the difference between the evaluations of actions �
and � for criterion �� (Behzadian, et al, 2010).
Step 2 is to application of the preference functions of each criterion. This allows for differing
criteria values to be calculated as a preference degree, through the Equation 2.
��(�, �) = �����(�, �)� � = 1, … ,�
Where �� is the preference of the alternative � compared to the alternative � for each criterion
� as a function of ��(�, �) (Behzadian, et al., 2010).
Following this, PROMETHEE II then calculates the overall performance index using Equation 3.
33
∀�, � ∈ �, �(�, �) = ∑ ��(�, �)�����
Where �(�, �) of � over � (from 0 to 1) is defined as the weighting sum for each criterion and
� is the weight associated with the �th criterion. (Behzadian, et al., 2010)
Step 4 sees the tool calculate the positive and negative outranking flows. In the case of the
positive ranking flows, the calculation considers how much scenario � is preferred over the other scenarios. The negative ranking flow calculates how much the other scenarios are
preferred to scenario � (Haralambopoulos et al, 2003). The following equations illustrate this, respectively.
�(�) =�
���∑ �(�, �)�∈� and Ø�(�) =
�
���∑ �(�, �)�∈�
Where �(�)denotes the positive outranking flow and �(�) denotes the negative
outranking flow for each alternative (Behzadian, et al., 2010).
The ultimate step is to calculate the difference between the positive outranking flow and the
negative outranking flow to obtain the net outranking flow. This is shown in the Equation 6
Ø(�) = Ø + (�) − Ø − (�)
Where Ø(�) denotes the outranking flow for each alternative (Behzadian, et al., 2010.
34
4. Project Description
4.1. Introduction
To evaluate the benefits and barriers of remanufactured turbines, the author has decided to
use the MCDA tool PROMETHEE II to compare multiple scenarios which include new and
remanufactured turbines. This tool was selected due to its ability to evaluate conflicting
quantitative and qualitative criteria, as well as utilising a straightforward method, resulting in
a clear outcome. The aim is to make use of the information gathered in the literature review
and draw a conclusion on whether there is potential for remanufactured wind turbines within
the wind energy industry as well as assessing MCDA as a decision-making tool. This chapter
presents a theoretical case study in which the project is solely based around the selection of a
wind turbine which could provide a solution to the future decommissioned material within the
industry as well as the need for medium scale wind turbines.
4.2. Case Study
As the focus of this project is based around the turbine selection process, there was no need
to choose a specific site, instead some boundaries that have been assumed for all scenarios
have been selected by the author, based on research of literature and available data. The
medium scale market usually consists of wind turbines with a capacity ranging from 500kW
to 1.5MW, however, this study will investigate a turbine of 2MW capacity, as this is the most
commonly presented in Life Cycle Analysis (LCA) literature.
4.3. Life Cycle Analysis Review
The first step of the project was to access multiple LCA’s of 2MW turbines, with the aim of
gathering a clearer picture on the average figures in focused areas. Six publications were
reviewed and a description of the information gathered is presented below (Garrett et al, 2012.,
Martinez et al, 2010., Vargas et al, 2015., Guezuraga et al, 2012., Ghenai, 2012., Vesta 2011).
• Performance: a clearer picture on the overall performance of a 2MW wind turbine was
required so that the author could make an accurate assumption on electricity
generation. Whilst it is understood there is an abundance of factors contributing to
35
the performance of a wind turbine, this project simply requires a best guess figure
for consistency throughout.
Average lifetime: an understanding of the average service life of the wind turbines
in the LCA’s was required.
Bill of components: a list of the major components considered in LCA’s was then
required.
Bill of materials: a list of the material type as well as the average mass of material
in the LCA’s was calculated.
Once all the necessary information was gathered, a table of the averages of the data sets
listed was created; this is represented in Tables 2 and 3.
Table 2:Summary of components and average mass from LCA’s reviewed.
Capacity (MW)
Lifetime (Years)
Components Sub-component
Component Mass (Tonnes)
2 20 Rotor Three blades 22
Hub 9
Tower - 153.6
Nacelle Main Shaft 9.05
Transformer 7.5
Generator 8.25
Others 8.75
Gearbox 18
Nacelle Cover 3
Table 3:Summary of materials and average material mass from LCA's reviewed.
Material Material Mass (Tonnes)
Mass %
Steel 202.35 72%
Cast Iron 39.25 14%
Copper 5.25 2%
Fiberglass 18.11 6%
Resin 13.08 5%
Aluminium 2 1%
TOTAL 280.04 100%
36
4.4. Scenarios
The aim of this project is to compare the implementation of a remanufactured wind turbine
against that of a new wind turbine and as a result the author has created three scenarios
which is felt best suit the study, taking in to consideration the information gained from the
literature review. A list of these scenarios can be found below:
Scenario 1: A new wind turbine of 2MW capacity.
Scenario 2: A remanufactured turbine of 2MW capacity, with cost of remanufactured
components set at 50% of the manufacturing cost, energy needed remanufacture
components set at 50% of energy to manufacture, and Co2 produced during remanufacturing
set at 50% of Co2 produced during manufacturing. The values for this scenario were assumed
in relation to the literature reviewed on remanufactured products from multiple industries
(Kerr et all, 2001., Golinska et al, 2011., Li et al, 2013., Sutherland et al, 2008., Seitz, 2007).
Scenario 3: A remanufactured turbine of 2MW capacity, with cost of remanufactured
components set at 70% of the manufacturing cost, energy needed remanufacture
components set at 70% of energy to manufacture, and Co2 produced during remanufacturing
set at 70% of Co2 produced during manufacturing. (reference). This
scenario was created to offset the assumptions gained from the literature in scenario 1; the
cost to remanufacture was chosen due to literature which concluded that a new product
would be preferred over a remanufactured product if costs were to exceed 70% of the new
one.
Several factors which remain constant throughout the scenarios for consistency are as
follows:
• A service life of 20 years.
• AEP of 4660 MWh per year, using a capacity factor of 26.6% (Renewable UK, 2017).
• O&M costs of 2% of the initial turbine investment.
• The components for remanufacturing are tower, rotor, nacelle cover and bedframe.
• The components to be replaced are the gearbox, generator, transformer and main
shaft.
• Full recycling of materials of components which can be recycled at end of service life.
37
5. Stakeholder Selection The stakeholder selection process considered those who would have a significant role in
the consideration of both scenarios, direct or indirect, and the possible influence that they
may have on the outcome. The selection of the stakeholders was conducted based on the
authors assumptions as a result of the literature review conducted. A list of the selected
stakeholders is provided below and an explanation of their involvement in the sub-
sections that follow.
1. Investor
2. Developer
3. Public
4. Environmental NGO
5. Manufacturer
6. Governmental Body
5.1. Investor
Investors involvement in development of wind power is paramount as they are the main
source of financial input. They will usually be consulted with all decisions regarding the
development of the project and their focus is on the economic aspect. When considering the
wind turbine options they are looking for performance and reliability, essentially looking for
a minimal risk and maximum profit.
5.2. Developer
The developer’s role is to complete a project to a high standard in the shortest possible time-
frame and although the focus of the developer is to meet such targets, they must also
consider all other impacts that a project can have, both socially and environmentally. The
choice of turbine will inevitably come down to their decision, however they are inclined to
keep all parties involved happy throughout the project and therefore must carefully consider
their opinions.
38
5.3. Public
As the case scenario is not specifically tied to one site, the public are not being constrained to
a scale. Instead they will be used as a general opinion for the two scenarios, with the author
understanding that they would need to be considered and informed of such a decision in
most relevant cases. Their focus will be on lower electricity price as well as an overall concern
for the environment effects of the decision.
5.4. Environmental NGO
In this case, the environmental NGO is a charitable body that aims for continuous improvement
of sustainability. Although they have no direct input to a single wind power project, they do
have a strong voice within renewable energy, so it seems appropriate to consider them when
undertaking this MCDA. Their focus is to inspire the re-thinking of product design aiming for
sustainability through the minimisation of waste, minimisation of Co2 needed to produce the
product, and reduction on energy usage. The Ellen McArthur Foundation has been mentioned
previously in this paper and can be referred to for an example.
5.5. Manufacturers
The manufacturers are focused on maximising their own profit on sale whilst also aiming
for continual improvement and growth of the market. They also have a duty to minimise
the effects their process has on the environment through legislation, so this will be of
concern to them.
5.6. Governmental body
The concern of the Governmental Body is to ensure a projects outcome is best suited to
all the stakeholders involved. Aiming to build upon a sustainable society through the
economic, social and environmental planning whilst adhering to energy policies and
striving to meet the targets that are set out. This stakeholder can easily be applicable to
the EU-wide 2030 targets.
39
6. Evaluation Criteria
One of the main benefits of using MCDA, is the ability to compare data on a level form in ways
that may not have been attainable otherwise; this allows the author to evaluate multiple
factors, which is beneficial when attempting to provide as thorough a conclusion as possible.
This report looks at the key drivers in sustainable development, which are the economic,
environmental and social factors. Due to the nature of wind power, and for the purpose of
this report, the author has decided to include technology as a fourth factor which will attempt
to compare the criteria which is deemed to be important to the topic of remanufacturing
specifically, thus, making it more scientifically beneficial. The author has gone on to select
sub-criteria within each category, making it relevant to the research.
6.1. Economic Criteria
The economic criterion is comprised of the sub-criteria Manufacturing Costs and Net Present
Value. Further details on these sub-criteria is explained in the following sections.
6.1.1. Manufacturing Costs
As the focus of this paper is on the comparison of using a new wind turbine against a
remanufactured turbine in wind power development, it is important to consider the
respective costs for each. The data for this has been sourced from the multiple Life Cycle
Analysis papers the author has reviewed.
The manufacturing costs take in to consideration the extraction of material, cost of
transportation and the cost to process the material, and is calculated in EURO (€). The total
cost for a 2MW turbine was assumed to be €321,000 taken from the NREL (2015) report. The
percentage of total cost to manufacture a wind turbine are estimated in the NREL (2015)
report and so the value of 71% to manufacture a new turbine was used for this paper. For the
remanufactured turbine, the research conducted for this study presented an average cost
saving of 50% and so this was used in the calculation of scenario 2. As Scenario 3 looks at the
possibility of a higher cost to remanufacture, a value of 70% was chose by the
author in accordance with the research that suggested a new product will be preferred if
the remanufactured product costs more than 70% of a new product (Gan et al 2017).
40
6.1.2. Net Present Value
Net Present Value (NPV) is the variance in all income and expenditures of the lifetime of a
project. In order for the project to be considered profitable, the NPV must be positive and it
is therefore preferred for this value to be as high as possible. Since NPV has been widely used,
author has chosen Excel to calculate the NPV of the scenarios presented in this paper and the
lifetime was assumed to be 20 years in all scenarios for consistency.
6.1.3. Environmental Criteria
The environmental criterion looks at various impacts that are deemed important to consider
when evaluating both scenarios. The sub-criteria consist of: Material Circularity Indicator,
Energy to Manufacture and Co2 to Manufacture. Further details on these sub-criteria is
explained in the following sections.
6.1.4. Material Circularity Indicator
Material Circularity Indicator is a tool developed by the Ellen MacArthur (2015), which aims
to measure the minimisation of a products linear flow and maximise its restorative flow for
all the component materials. This provides a clearer indication of the sustainability of a
product by looking at how much of the material is virgin, reused or recycled. It is presented
as a quantitative figure between 0 and 1, with a maximum output preferred.
The calculation measures a products MCI by considering the percentage of virgin material,
percentage of unrecoverable waste and the utility factor of the product, which is the product
lifetime and intensity its of its use. For a new wind turbine, it is assumed that the product is
made up entirely of virgin material, however, for all virgin materials a recycling fraction is
incorporated; this is an estimation of the proportion of a material in use worldwide has been
recycled and allows. It is also considered that all materials in the new turbine which can be
effectively recycled at the end of the products life, will be with relative efficiency. The
remanufactured turbine is comprised of both new and reused material, therefore to account
for this, the fraction of materials which are used in new components will be considered in the
same way as the new turbine. All reused materials will therefore
41
have maximum MCI. To get an overall MCI for the product, an aggregate of the MCI for
the mass of each component is calculated. Firstly, the virgin material of the product is
calculated using the following equation:
� = �(1 − �� − ��)
Where � is the mass of finished product ��, is the fraction of feedstock obtained from
recycled sources and is the fraction of feedstock obtained from reused sources.
As all scenarios of this study are assumed to be collected for recycling where possible;
unrecoverable waste, �� , from the recycled material is calculated as:
�� = ��(1 − ��)
Where � is the mass of the �th material and �� is the recycling efficiency of the nth
material.
As it is assumed that a fraction of the feedstock material was obtained from recycled
sources, the calculation of unrecoverable waste, ��,is as follows:
�� = ��
(1 − ��)
��
When calculating the total mass of unrecoverable waste, adding �� and , would result in
some of the unrecoverable waste being double counted. To avoid this the following equation
is necessary:
�� = (�� − ��)
2
The next step is to calculate the Linear Flow Index (LCI), which takes in to consideration how
much material is flowing in a linear take-make-dispose fashion, as described in section 2.6. LFI
is presented with a value between 0 and 1, where 1 is an entirely linear flow. The equation
for LFI is as follows:
��� = � − �
2� +(�� − ��)
2
Finally, the Material Circularity Indicator can be obtained:
42
��� = 1 − ���(�(�))
Where � is the function of utility . As this study only considers one service lifetime of a
wind turbine, F(X) = 1.
6.1.5. Energy to Manufacture
The processes used to manufacture a turbine require a great deal of energy; as we aim to
become more sustainable in the way we produce products it is important to consider how
much energy is needed to do so, striving for efficiency. It is easy to overlook the energy used
to manufacture a turbine as it has the benefit of being able to “payback” this energy during
its lifetime. This criterion considers the energy used solely on the
manufacturing/remanufacturing process. Using information provided from the LCA’s
researched from this paper a calculation of the energy needed was conducted by considering
the mass of the materials used and their relative embodied energy; the energy consumed by
all processes necessary for production. The indirect energy, the energy needed for
manufacturing, was then calculated and provided in MJ, with a minimum value preferred. The
total energy to manufacture, ��, is described in the equation:
�� = ����� + ����� + ⋯
Where EE is the embodied Energy for the nth material and m is the materials mass for the
nth material.
Due to the lack of research conducted on remanufacturing of wind turbines, the author has
turned to research papers of other remanufactured products such as automotive engines,
printing cartridges and electronic components. Similar findings were also published in the
paper by Ortegon et al 2012, which has been used as further reference to the calculations.
From this, an average of 50% of energy used was used for the components that are to be
remanufactured in Scenario 2 and Scenario 3. Similar consideration was taken for the
components which go through a high amount of wear and tear during the first life of the
wind turbine. These components are paramount to the reliability of the turbine and so for
the purpose of this paper they will be replaced. These components are the gearbox,
generator, transformer and main shaft.
43
6.1.6. Co2 to Manufacture
Co2 is inevitable when manufacturing new product but as the global outlook is focused on
reducing the Co2 levels and governments are aiming to meet targets, it is important to access
the levels we produce as a by-product. This criterion has been selected to evaluate the
significance in both scenarios. In principle, the Co2 to manufacture is calculated in the same
way as energy to manufactured but its provided in kgCo2, with a minimum value preferred.
The same assumptions for the replacement of certain components will be transferred to
these calculations. The total Co2 to manufacture is described in the following equation, where
EC1 is the embodied Co2 for the nth material and m is the materials mass for the nth material.
� = ������ + ����� + ⋯
6.2. Technical Criteria
The Technical criterion has been introduced to gain an understanding of its significance
on the development of a wind project. The sub-criteria consist of Availability, Risk and
Lead Time.
6.2.1. Availability
The increase in wind power development must be met with an increase in wind turbine
manufacturing; developers have a magnitude of turbine options when it comes to selecting one
and although there are many aspects to consider when doing so, namely performance at an
individual site, the availability of the turbine is paramount to ensure a smooth and fast project.
Whilst there is an abundance of new turbines, making availability less of a concern, this criterion
has been selected to consider the effect that the current availability and
variety of remanufactured turbines may pose of the selection process. As noted in the
literature, although there is a market potential for medium scale turbines, the production has
depleted due to the development of new turbine technology (Ortegon et al, 2012., Parker et
44
al, 2008). Due to the lack of quantitative data available to the author regarding wind turbine
availability, this criterion will not present the estimated value of how many 2MW wind
turbines are available for each scenario. Instead, the unit will be scaled between 1-10 with
the authors judgement on the current availability with a maximum value preferred.
Table 4: Scale of Turbine Availability
Scale Availability
1-2 Few
3-5 Few to Some
6-7 Some to Widespread
8-10 Widespread
6.2.2. Risk
All wind power projects will undergo multiple risk analyses throughout the project. The main
aim of these assessments is to minimise the economic risk of a project which can happen for
many reasons such as delays, change in project value (i.e. drop in electricity price or subsidy
cuts), or social and environmental impacts. When considering the turbine selection itself, a risk
analyses is much harder to predict and mitigate. The main problem lies within the performance
of the turbine throughout its lifetime. Although a deterioration in turbine performance is
expected, it is the failing or radical underperforming risk that can cause great problems.
Manufacturers offer warranty as well as operation and maintenance packages to ensure their
turbines reliability and this criterion has been selected to address the grey area of the risk of
remanufactured turbines. A scaled value between 1-10 has been selected by the author, taking
in to consideration the performance, reliability, warranty, maintenance. A minimum value is
preferred.
6.2.3. Lead Time
The lead time is the length of time between the initiation and completion of the product. For
manufacturing of a new turbine, this relates to the time taken This includes the extraction and
processing of the raw materials, transportation to the site, manufacturing and assembly of the
wind turbines components. The lead time for remanufacturing differs as it involves the
transportation of used turbine, disassembly, inspection, cleaning, remanufacturing or
45
replacement and assembly. It should be noted that although lead time could also fall under one
of the previous two criteria, the author has chosen it as a separate criterion as a result of the
literature review conducted. It is suggested that the lead time for a remanufactured turbine is
less than three months (repoweringsolutions.org, 2017., PES Wind, 2017) whereas a new
turbine can be anything from 12 to 16 months NREL (2004). The unit for this criterion is months
and a minimum value is preferred.
6.2.4. Product Development
The current development of wind turbines focuses on the improvement of performance; this
is not only evident in the increase in size of wind turbines over the years but also the
development of blade efficiency and the durability of components to meet varying
environmental demands. However, as this paper is focused on the sustainability of wind
energy, this criterion has been selected as a way of applying the findings which suggest
remanufacturing would encourage product design through greater product utilisation taking
in to consideration factors such as life extension, design for disassembly and design for repair
(Ellen McArthur Foundation 2015., Charter et al, 2008). A qualitative scale between 1-10 has
been used for this criterion, with a maximum value preferred.
Table 5: Scale of Encouragement of Sustainable Design
Scale Encouragement of Sustainable Design
1-2 Little
3-5 Little to Some
6-7 Some to Great
8-10 Great
6.3. Social Criteria
As the main aim of this paper is to consider the options of comparing the benefits of a
new turbine against that of a remanufactured one, there are fewer social aspects that are
relevant. One that does stand out however, is the perceived quality of a wind turbine in
both scenarios and this sub-criterion is explained in below.
46
6.3.1. Perceived Quality
The author has researched papers that involved the perception of the remanufacturing process
and its effect on decision making. As for now, the ambiguity of the remanufacturing process is
thought to have an adverse effect on consumer’s perception, resulting in them not seeing
equality between new and remanufactured products (Hazen 2016., Keoleian, 2004). Although
the other sub criteria may have a more important impact on the development of wind energy,
it is important to consider the stakeholders’ perception in all scenarios, as this would no doubt
play a significant role in the outcome of a project. Again, this is provided as a qualitative 1-10
scale with a maximum value preferred.
Table 6: Scale of Perception of Quality
Scale Perception of Quality
1-2 Very Low
3-5 Low to Medium
6-7 Medium to High
8-10 Very High
6.4. Summary of Criteria
Table 7 presents the results from the calculations carried out for each criterion as mentioned
in Section 6.
Table 7: Summary of Criteria
Criteria Sub-Criteria Unit Direction Scenario 1 Scenario 2 Scenario 3
Economic criteria
Manufacturing Cost
€ Min 2,279,100 1,139,550 1,595,370
NPV € Max 542,522.64 1,617,569.81 322,852.52
Environmental criteria
MCI Qualitative Scale 1-10
Max 6.6 9.5 9.5
Energy to Manufacture
[MJ] Min 13,750.25 6,875.12 6,875.12
Co2 to Manufacture
KgCo2 Min 1,068.08 534.04 534.04
Technical Criteria
Availability Qualitative Scale 1-10
Max 10 3 3
Risk Qualitative Scale 1-10
Min 2 7 8
Lead Time Months Min 36 6 6
Product Development
Qualitative Scale 1-10
Max 2 9 9
Social criteria Perceived Quality
Qualitative Scale 1-10
Max 10 3 2
7. MCDA Results
In this chapter a graphical representation of the results from the MCDA are presented, with
each graph illustrating the preference of its respective stakeholder.
Firstly, the results of the investor are presented in Figure 7, which shows that their preference
is towards Scenario 2, with scenario 3 being least preferred.
Figure 8 represents the preference of the developer and in this case, scenario 1 is most
preferred and scenario 3 the least.
12
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Figure 7: Preference of Investor
Figure 8: Preference of Developer
The results for the public, in figure 9 show that the preferred scenario is scenario 2, with
scenario 1 being least preferred.
In figure 10, the preference of the Environmental NGO can be seen. Whilst scenario 2 is the
most preferred, it’s worth noting that scenario 1 was the least preferred by a large margin.
1 23
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Figure 9: Preference of Public
Figure 10: Preference of Environmental NGO
In the case of the manufacturer, the preferred scenario is scenario 2, with 3 being least
preferred. This can be seen in figure 11.
The preference of the governmental body is presented in figure 12, with scenario 3 being
most preferred and scenario 1, the least preferred.
1 23
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Figure 11: Preference of Manufacturer
Figure 12: Preference of Governmental Body
Finally, Figure 13 is a representation of the preferred scenario when considering all the
stakeholders involved. As can be seen Scenario 2 was the most preferred and scenario 1 the
least.
Figure 13: Summary of preferred scenarios
8. Discussion
8.1. Introduction
In this chapter, the results presented in chapter 7 will be discussed. Focus will be placed
on the reason behind each stakeholder’s preferred scenario with similarities between the
stakeholders considered.
8.2. Analysis
From the results, it is noted that four out of six stakeholders preferred scenario 2, which was
the remanufactured turbine, which would be remanufactured at 50% of the cost, energy and
Co2 produced. Scenario 1, the newly manufactured turbine, was preferred by one
stakeholder and scenario 3, the wind turbine remanufactured at 70% of the cost was also
preferred by one stakeholder. On initial review, the reduced costs and environmental benefits
have been the reason behind the preference of scenario 1, however it must be noted that the
one stakeholder’s preference towards scenario 3 was unanticipated and suggest some
inconsistency with the other results.
The investors preferred scenario was scenario 2, which suggest that the potential for a smaller
initial investment, met by a greater net present value were the main factors in the outcome.
However, the margin between scenarios was minor, and with scenario 1 being the second
preference, this indicates that there has been an influence of ‘willingness to pay’ from the
investor, where the risk of investment was maybe not met by the value of return and perceived
quality may have been the deciding criterion. The developer preferred scenario 1 which is most
likely down to the concern about the current availability of remanufactured wind turbines,
which could pose a threat to the time scale of their project. Less concern for the reduction in
energy and Co2 during manufacture is another reason why Scenario 1 has come out on top. It
is fair to note that while the public have a growing concern for the impact we have having on
our environment, the main pull for them when it comes to energy generation is the reduction
in electricity costs; Scenario 2 was the preferred scenario for the public due to the reduced
project costs and while that does not necessarily imply that electricity costs will be reduced, it
certainly shows potential for doing so. Scenario 3 was given higher preference than scenario 1,
suggesting that the 70% cost to remanufacture
met the ‘willingness to pay’ bracket as suggested by the studies presented in the literature
review (Gan et al 2016). The results for the Environmental NGO were unsurprising with
Scenario 2 being preferred. The reduction in energy and Co2 during manufacture are
influential factors, but the Scenarios tendency towards a more circular economy, product
lifetime extension and product development, were certainly the driving factors for this
stakeholder. The manufacturer also took preference to Scenario 2, likely due to the potential
for larger profit margins; a reduction in manufacturing costs allow for economic growth and
driving a more competitive market. The shorter lead time for remanufactured turbines was
also important to the manufacturer, allowing for higher turnover of business. The reduction
of energy and Co2 to manufacture would allow for the manufacturer to meet any
environmental targets set out by the company or the municipality. Finally, the results of the
Governmental body show that scenario 3 would be the preferred scenario, which displays
some irregularity in the results. Scenario 3 was chosen this study to act as a variance of the
cost assumptions made, with the intention that it would define a range in which
remanufactured wind turbines would be accepted. It was not expected that it would achieve
a higher preference than scenario 2 from any of the stakeholders and so suggest some
inconsistency. Nonetheless, the preference towards remanufacturing would suggest that
high importance is placed on the reduction in environmental impact of the wind energy
industry, with EU targets being the focus for this stakeholder.
8.3. Limitations
To carry out this study, the author has had to make number of assumptions. Due to the lack
of research directly involving remanufacturing of wind turbines, studies from other
remanufacturing industries have been used. The weighting of the criteria for each stakeholder
was created by the author as there was a lack of information available from stakeholders in
the field, and for consistency is was deemed appropriate to make all assumptions. Any
assumptions of data have been provided in the relevant sections.
9. Conclusion
9.1. Summary of the study
Due to the rapid growth of the wind energy market over the last decade, the future of the
industry will consequently see the dismantling of many wind turbines, both due to wind
turbines reaching the end of their service life and to make way for surpassing technology,
leaving behind a large amount of material that must be dealt with. It is estimated that total
waste material will increase an average of 12% per year between 2014 and 2026 and 41% per
year between 2026 and 2034 (Andersen et al, 2016). Furthermore, due to the advancing
technology of wind turbines, there has been a decline in the number of medium sized wind
turbines being manufactured. This aim of this study was to address the problem of future waste
mitigation, whilst attempting to capture the medium scale market. As such, the study has
looked at the idea of a circular economy, in which wind turbines are not considered as waste at
the end of their service life, but rather an opportunity to recapture value through
remanufacturing. This was approached by identifying the driver and barriers of remanufactured
products, utilising knowledge from other industries with developed remanufacturing sectors.
From this a Multi-Criteria Decision Analysis has been performed using the PROMETHEE II
method. The aim was to draw a comparison of three scenarios, enveloped by a theoretical wind
turbine selection project. The scenarios were created by the author and considered the
implementation of a new wind turbine and remanufactured wind turbines, with the criteria
selected to address the need to reduce waste within the wind energy industry whilst capturing
the medium scale market potential. The study has shown that there is great potential for
remanufacturing within the wind industry, not only due to the economic potential of
developing the secondary market within the industry and driving competition, but as a means
of developing wind energy whilst focusing on the most important reason for its
implementation, the growth towards a sustainable future. Throughout the study it has been
noted that remanufacturing costs are estimated to be, on average, 50% of the cost to
manufacture a new turbine. However, the development of wind turbine technology is driving
the reduction in wind turbines costs annually whilst the cost to remanufacture will most likely
not decrease unless the market grows substantially. This could lead to further implications for
its development as most developers of wind would
opt for new wind turbines, rather than remanufactured models. However, the need for
medium size turbines is still relevant and many factors, including restrictions on wind turbine
size at specific sites, could allow for the development of remanufacturing to be achieved. It is
worth noting that whilst legislation for waste management is being implemented, it is currently
more of a guideline procedure on how to minimise the impact waste has on the environment.
If there is to be a drive towards an economy which is circular, then further legislative action
should be implemented to put greater responsibility on those who are designing,
manufacturing and buying products. In the case of wind energy, this responsibility should
stretch back to the manufacturer; currently a wind turbine manufacturers responsibility, and
subsequent handling of the material is absorbed by the customer once the product has been
delivered, leaving the manufacturer with less incentive to design a product which can be reused
or remanufactured easily. The competitive nature of the industry can also be a barrier, as
manufacturers are very secretive of the technology they have, and are developing. Whilst this
is understandable in a market that is growing the way wind energy is, it somewhat suffocates
the potential for overall development.
9.2. Future Research
As this study attempted to look at the potential for remanufacturing within the wind energy
industry, it was noted that there are multiple areas that must be researched for its
development. Firstly, a greater understanding of the remanufacturing process of a wind
turbine, including all components which are suitable for remanufacturing should be
researched thoroughly. In turn this would allow for accurate data regarding the costs to
remanufacture and energy saving made. With more accurate data available, the use of an
MCDA to compare new and remanufactured turbines could be improved. Studies in to the
perceived quality of remanufactured wind turbines would help identify barriers that would
need to be addressed for the development of a secondary market. Finally, research in to the
design of wind turbines which aim at extending the lifetime of materials and components
would benefit the transition towards a more circular economy.
10. References • Aldén, L., Ansén Nilsson, M., Barney, A., & Ekman, M. E. (2014). Nedmontering av • Andersen, N., Eriksson, O., Hillman, K. and Wallhagen, M. (2016). Wind Turbines’ End-
of-Life: Quantification and Characterisation of Future Waste Materials on a National Level. Energies, 9(12), pp.1-24.
• Andersen, P., Borup, M. and Krogh, T. (2007). Managing long-term environmental aspects of wind turbines: a prospective case study. International Journal of Technology, Policy and Management, 7(4), pp.339-354.
• Atasu, A., Guide, V. and Van Wassenhove, L. (2008). Product Reuse Economics in Closed-Loop Supply Chain Research. Production and Operations Management, 17(5), pp.483-496.
• Behzadian, M., Kazemzadeh, R., Albadvi, A. & Aghdasi, M., 2010. PROMETHEE: A comprehensive literature review on methodologies and applications. European journal of Operational research, 200(1), pp. 198-215.
• Bloomberg New Energy Finance. (2017). BNEF 2016 wind turbine manufacturers ranking. [online] Available at: https://about.bnef.com/blog/vestas-reclaims-top-spot-annual-ranking-wind-turbine-makers/ [Accessed 21 Nov. 2017].
• Brans, J., Vincke, P., Mareschal, B., 1986. How to select and how to rank projects: The PROMETHEE method. European journal of operational research, 24(2), pp. 228-238.
• Carter, C.R. & Rogers, D.S., 2008. A framework of sustainable supply chain management: moving toward new theory. International Journal of Physical Distribution & Logistics Management, 38(5), pp.360–387
• Caterpillar.com. (2017). The Benefits of Remanufacturing. [online] Available at: https://www.caterpillar.com/en/company/sustainability/remanufacturing/benefits .html [Accessed 25 Nov. 2017].
• Charter, M., Gray, C., 2008. Remanufacturing and product design. International. Journal of Product Development 6 (3e4), pp. 375-392.
• Climate Action - European Commission. (2017). 2030 climate & energy framework - Climate Action - European Commission. [online] Available at: https://ec.europa.eu/clima/policies/strategies/2030_en [Accessed 21 Nov. 2017].
• Cooper, T. (1994). Beyond recycling: the longer life option. London, New Economics Foundation. P.5.
• Cooper, T. (2010). Longer Lasting Products: Alternatives To The Throwaway Society. UK: Gower Publishing. P.9
• Elkington, J. (1998). Cannibals with forks: The triple bottom line of 21st century business. Gabriola Island, BC Canada: New Society Publishers.
• Ellen Mcarthur Foundation (2014) Towards the Circular Economy 3: Accelerating the Scale Up. Available at: https://www.ellenmacarthurfoundation.org/publications
• Ellen McArthur Foundation (2015) Growth Within: A Circular Economy Vision for a Competitive Europe. Available at: https://www.ellenmacarthurfoundation.org/publications
• Ellenmacarthurfoundation.org. (2017). Circular Economy - UK, USA, Europe, Asia & South America - The Ellen MacArthur Foundation. [online] Available at: https://www.ellenmacarthurfoundation.org/ [Accessed 25 Nov. 2017].
• Gan, S., Pujawan, I., Suparno and Widodo, B. (2017). Pricing decision for new and remanufactured product in a closed-loop supply chain with separate sales-channel. International Journal of Production Economics, 190, pp.120-132.
• Garrett, P. and Rønde, K. (2012). Life cycle assessment of wind power: comprehensive results from a state-of-the-art approach. The International Journal of Life Cycle Assessment, 18(1), pp.37-48.
• Georgopoulou, E., Lalas, D., Papagianakis, L. (1997) A Mullticriteria decision aid approach for energy planning problems: the case of renewable energy option. European Journal of Operational Research 103, 483-500.
• Ghenai, C., 2012. Life Cycle Analysis of Wind Turbine, Sustainable Development - Energy, Engineering and Technologies - Manufacturing and Environment, Prof. Chaouki Ghenai.
• Glavič, P. & Lukman, R., 2007. Review of sustainability terms and their definitions. Journal of Cleaner Production, 15(18), pp.1875–1885.
• Green Energy and Technology, pp. 7-10. • Guezuraga, B., Zauner, R. and Pölz, W. (2012). Life cycle assessment of two different 2
MW class wind turbines. Renewable Energy, 37(1), pp.37-44. • Guide, V. D. R. and van Wassenhove, l. N. (2001), Managing Product Returns for
Remanufacturing. Production and Operations Management, 10: 142–155. • Haralambopoulos, D., Polatidis, H., 2003. Renewable energy projects: structuring a
multi-criteria group decision-making framework. Renewable energy, 28(6), pp. 961-973.
• Hatcher, G., Ijomah, W. and Windmill, J. (2011). Design for remanufacture: a literature review and future research needs. Journal of Cleaner Production, 19(1718), pp.2004-2014.
• Hazen, B.T., 2011. Strategic reverse logistics disposition decisions: from theory to practice. International Journal of Logistics Systems and Management 10 (3), 275– 292.
• Hazen, BT., Boone, C., Wang, Y., Khor, KS. (2016). Perceived Quality of Remanufactured Products: Construct and Measure Development. Journal of Cleaner Production, pp. 716-726.
• Henriques, A. and Richardson, J. (2005). The triple bottom line, does it all add up?. London: Earthscan, p.1.
• Hubbard, G., 2009. Measuring organizational performance: beyond the triple bottom line. Business Strategy and the Environment, 18(3), pp.177–191.
• Ijomah, Winifred L., 2010. The application of remanufacturing in sustainable manufacture. Proceedings of the ICE - Waste and Resource Management, 163(4), pp.157–163. Available at:
• Ijomah, WL., Childe, S., McMahon, C (2004). Remanufacturing: a key strategy for sustainable development. in Proceedings of the 3rd International Conference on Design and Manufacture for Sustainable Development. Pp.712-719.
• J. R. San Cristóbal Mateo., 2012 Multi-Criteria Analysis in the Renewable Energy Industry, 7
• Johnston, P. Et al., 2007. Reclaiming the definition of sustainability. Environmental science and pollution research international, 14(1), pp.60–61.
• King, A., Burgess, S., Ijomah, W. and McMahon, C. (2006). Reducing waste: repair, recondition, remanufacture or recycle?. Sustainable Development, 14(4), pp.257-267.
• Living Planet Report 2016. (2017). [ebook] Global Footprint Network, p.3. Available at: http://wwf.panda.org/about_our_earth/all_publications/ecological_footprint2/[Accessed 21 Nov. 2017].
• Martínez, E., Jiménez, E., Blanco, J. and Sanz, F. (2010). LCA sensitivity analysis of a multi-megawatt wind turbine. Applied Energy, 87(7), pp.2293-2303.
• Mcdonough, W., Braungart, M. (2002). Cradle to cradle: remaking the way we make things. New York, North Point Press.
• NREL, (2004). An Analysis of the Technical and Economic Potential for Mid-Scale Distributed Wind,. National Renewable Energy Laboratory, Farifax, Virginia.
• Nrel.gov. (2015). Cite a Website - Cite This For Me. [online] Available at: https://www.nrel.gov/docs/fy17osti/66861.pdf [Accessed 26 Nov. 2017].
• Ortegon K., Nies L.F., Sutherland J.W. (2012) Remanufacturing: An Alternative for End of Use of Wind Turbines. In: Dornfeld D., Linke B. (eds) Leveraging Technology for a Sustainable World. Springer, Berlin, Heidelberg pp.156-160.
• Ortegon, K., Nies, L. and Sutherland, J. (2014). The Impact of Maintenance and Technology Change on Remanufacturing as a Recovery Alternative for Used Wind Turbines. Procedia CIRP, 15, pp.182-188.
• Parker, D., Walton, S. (2008). The Potential for Remanufacturing of Wind Turbines. Centre for Remanufacture and Reuse.
• PES Wind, (2017). [ebook] Turbine transformation – a new lease of life for ageing wind turbines., p.109. Available at: new.abb.com/.../wind-power.../turbine-transformation---a-new-lease-of-life-for-ageing-wind-turbines [Accessed 25 Nov. 2017].
• PLATE. (2017). Routes for extending the lifetime of wind turbines - PLATE. [online] Available at: http://www.plateconference.org/routes-extending-lifetime-wind-turbines/ [Accessed 25 Nov. 2017].
• Princen, T. (1999). Consumption and environment: some conceptual issues. Ecological Economics, 31(3), pp.347-363.
• Rees, W. and Wackernagel, M. (1996). Urban ecological footprints: Why cities cannot be sustainable—And why they are a key to sustainability. Environmental Impact Assessment Review, 16(4-6), pp.223-248.
• Renewableuk.com. (2017). Statistics Explained - RenewableUK. [online] Available at: http://www.renewableuk.com/page/UKWEDExplained [Accessed 26 Nov. 2017].
• Repoweringsolutions.com. (2017). refurbished wind turbine | Overhaul second hand wind turbines | Growing with the wind turbine. [online] Available at: http://www.repoweringsolutions.com/english/products/refurbished_wind_turbine/index.htm [Accessed 25 Nov. 2017].
• Repoweringsolutions.com. (2017). refurbished wind turbine | Overhaul second hand wind turbines | Growing with the wind turbine. [online] Available at: http://www.repoweringsolutions.com/english/products/refurbished_wind_turbine/index.htm [Accessed 26 Nov. 2017].
• Smith, V. and Keoleian, G. (2008). The Value of Remanufactured Engines: Life-Cycle Environmental and Economic Perspectives. Journal of Industrial Ecology, 8(1-2), pp.193-221.
• Souza, G.C., Ketzenberg, M.E., Guide Jr, V.D.R. (2002). Capacitated remanufacturing with service level constraints. Production and Operations Management 11 (2), 231–248.
• Stahel, W. (1998), “From products to services: selling performance instead of goods”, The IPTS Report, Institute for Prospective Technological Studies, Seville
• Statham, S. (2006). Remanufacturing Towards a More Sustainable Future, Electronics-enabled Products Knowledge-transfer Network.
• Sutherland, J., Adler, D., Haapala, K. and Kumar, V. (2008). A comparison of manufacturing and remanufacturing energy intensities with application to diesel engine production. CIRP Annals, 57(1), pp.5-8.
• Topham, E. and McMillan, D. (2017). Sustainable decommissioning of an offshore wind farm. Renewable Energy, 102, pp.470-480.
• Vargas, A., Zenón, E., Oswald, U., Islas, J., Güereca, L. and Manzini, F. (2015). Life cycle assessment: A case study of two wind turbines used in Mexico. Applied Thermal Engineering, 75, pp.1210-1216.
• Vestas, (2011). Life Cycle Assessment of Electricity Production from a V90-2.0 MW Gridstreamer Wind Plant.
• Vindkraftverk och efterbehandling av platsen. Stockholm: Energimyndigheten. P.17. • Walton, S, Parker, D, 2008. The potential for Remanufacturing of Wind Turbines. Centre
for Remanufacturing & Refuse Product Group Study, p5 • Wang, J., Jing, Y., Zhang, C. & Zhao, J., 2009. Review on multi-criteria decision analysis
aid in sustainable energy decision-making. Renewable and Sustainable Energy Reviews, 13(9), pp. 2263-2278.
• Wątróbski, J.; Sałabun, W., (2016) The characteristic objects method: a new intelligent decision support tool for sustainable manufacturing. In Sustainable Design and Manufacturing; Springer: Berlin, Germany; pp. 349–359.
• WCED, 1987. Our Common Future. World Commission on Environment and Development. Oxford University Press, Oxford. P.41.
• Welstead, J., Hirst, R., Keogh, D., Robb G. And Bainsfair, R. 2013. Research and guidance on restoration and decommissioning of onshore wind farms. Scottish Natural Heritage Commissioned Report No. 591.
• Wind in Power - 2016 European Statistics. (2017). [ebook] Wind Europe, p.7. Available at: https://windeurope.org/wp-content/uploads/files/about-wind/statistics/windeurope-Annual-Statistics-2016.pdf [Accessed 21 Nov. 2017].
• Windpowermonthly.com. (2017). Vestas signs remanufacturing deal with Caterpillar. [online] Available at: https://www.windpowermonthly.com/article/1102756/vestas-signs-remanufacturing-deal-caterpillar [Accessed 25 Nov. 2017].
• Scottish Government, 2008. legislation.gov.uk. [Online] Available at: http://www.legislation.gov.uk/ukpga/2008/32/pdfs/ukpga_20080032_en.pdf[Accessed 24 09 2017].
• Scottish Government, 2008. legislation.gov.uk. [Online] Available at: http://www.legislation.gov.uk/uksi/2008/314/pdfs/uksi_20080314_en.pdf [Accessed 03 10 2017].
• Scottish Government, 2010. Scotland's Zero Waste Plan. [Online] Available at: http://www.gov.scot/Resource/0045/00458945.pdf [Accessed 15 10 2017].